Coolant pump for a collant circuit of an internal combustion engine

ABSTRACT

A coolant pump for a coolant circuit of an internal combustion engine, including a drive wheel which is connected to an impeller via a drive shaft rotatably mounted in a pump housing has at least one coolant outlet provided radially with respect to the impeller. A blocking ring is movable in an axial direction and serves to change or block a cross-sectional area of the coolant outlet and is displaced by a pressure-medium-operated actuator. The actuator is arranged concentrically with the drive shaft in the region of the end thereof facing the impeller is secured on the end of the drive shaft, and is connected to a pressure medium supply via at least one longitudinal bore provided in the drive shaft.

The present invention relates to a coolant pump for a coolant circuit of an internal combustion engine, as defined in the preambles of the independent claims, the coolant pump including a drive wheel which is preferably driven by a belt drive and is connected to an impeller via a drive shaft rotatably mounted in a pump housing, at least one coolant outlet being provided radially with respect to the impeller, the coolant pump further including a blocking ring which is movable in an axial direction and serves to change or block a cross-sectional area of the coolant outlet, and further including a pressure-medium-operated actuator for displacing the blocking ring.

BACKGROUND

Coolant pumps of this type are typically in the form of centrifugal pumps and are disposed at the front end of the internal combustion engine and driven by one of the belt drives provided there. In this case, the drive shaft of the coolant pump rotates synchronously with the speed of rotation of the internal combustion engine and therefore delivers a certain amount of coolant, which is analogous to this speed of rotation, into the coolant circuit formed by the coolant chambers provided in the crankcase and in the cylinder head, a heat exchanger for a vehicle heating system, and a radiator traversed by cooling air. The coolant pump is designed to deliver the coolant flow required to provide sufficient cooling power under all operating conditions, even at idling speed of the internal combustion engine.

During the warm-up phase of the internal combustion engine, the coolant flow through the radiator is generally blocked, either completely or partially, by a thermostatic valve. In this phase, in which the internal combustion engine has not yet reached the intended operating temperature, the entire coolant flow or a partial flow is short-circuited by this thermostatic valve through a bypass line parallel to the radiator.

Also, in the past, efforts have already been made to significantly shorten this warm-up phase, whereby the frictional losses occurring during operation of the internal combustion engine and the increased fuel consumption levels and resulting increased emission levels can also be reduced to a significant extent. Provision was made, inter alia, to control the input speed of the coolant pump via a gear mechanism driving the coolant pump, or to completely enable or disable the entire drive of the coolant pump via a clutch. In other known approaches, the coolant pump, which is in the form of a centrifugal pump, is provided with adjusting elements which allow controlled adjustment of the outflow of coolant to the point of complete blockage. The present invention relates to a coolant pump having such a design.

A coolant pump for a coolant circuit of an internal combustion engine is known from DE 10 2007 022 189 A1. The coolant pump described therein is a controllable pump in which the guide plate is moved as a function of a negative or positive pressure transmitted to a pressure cell. This pressure cell is intended to function as a pressure intensifier, whereby the working fluid present in a hydraulic line is displaced into a plurality of slave cylinders of small cross section by means of a working piston of large cross section, which is disposed in the vacuum cell. These slave cylinders are arranged in the coolant pump housing such that they are uniformly distributed around the circumference thereof and each contain a piston rod. The ends of the piston rods facing away from an overflow chamber are connected to the axially movable valve spool. Instead of the vacuum control, which uses the negative pressure in an intake tract of the internal combustion engine, the working piston disposed in the pressure intensifier can also be acted upon by positive pressure from the lubricant circuit of the internal combustion engine.

Further, German Patent Application DE 199 01 123 A1 describes a controllable coolant pump in which an actuator is provided in the impeller for axially moving a sleeve which radially surrounds the coolant outlet. One of the embodiments shown provides that this actuator takes the form of a wax expansion element by which a pin extending in the longitudinal direction of the coolant pump is displaced and force is transmitted to the sleeve via a radially extending pin. This document further states that this actuator may also be operated electrically, hydraulically or pneumatically.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved coolant pump for a coolant circuit of an internal combustion engine, which coolant pump is provided with a blocking ring device controlling the coolant outlet, the improvement residing in that the actuator provided for the blocking ring device can be disposed inside the coolant pump without changing its overall dimensions in the radial or axial directions or only slightly modifying the same. Moreover, a controllable coolant pump provided with such an actuator should be inexpensive to manufacture and very reliable in operation, so that it can be used in a mass-produced internal combustion engine.

The present invention provides for the actuator to be disposed concentrically with the drive shaft in the region of the end thereof facing the impeller, to be secured on the end of the drive shaft, and to be connected to a pressure medium supply via at least one longitudinal bore provided in the drive shaft. Such an arrangement of the actuator and its pressure medium supply via a longitudinal bore in the drive shaft provide small overall radial dimensions for the housing of the coolant pump. Advantageously, the radial dimensions may substantially match the radial dimensions of the pulley driving the coolant pump. Moreover, this arrangement of the actuator has a positive effect on the axial dimensions, because by arranging the actuator at the end of the drive shaft, the overall length of the coolant pump housing remains nearly unchanged. This is very important because in the end-face region of the internal combustion engine; i.e., in the region of the belt drives thereof, only limited space is available for arranging and driving the coolant pump, and the coolant pump must be axially dimensioned such that its pulley is in alignment with the other pulleys.

In contrast, in German Patent Application DE 10 2007 022 189 A1, a plurality of hydraulic actuators in the form of individual piston/cylinder units are arranged within the housing of the coolant pump, the guide plate being secured to the plurality of hydraulic actuators. Due to the radial pressure medium supply to the individual actuators, and because the actuators are arranged in this way, unfavorable radial and axial dimensions are obtained for the housing of the coolant pump. Moreover, malfunctions can occur if the pistons of the piston/cylinder units do not perform absolutely synchronous longitudinal movements.

In German Patent Application DE 199 01 123 A1, in contrast to the approach of the present invention, the actuator is disposed in a hub of the impeller of the coolant pump and, therefore, is not located at the end of the drive shaft facing the impeller. Apart from that, it can only be inferred from this patent publication that an electrical, hydraulic or pneumatic adjusting mechanism may be used in place of the depicted wax expansion element. However, a corresponding supply of a hydraulic medium is quite obviously intended to be via the housing of the coolant pump. Both the actuator arrangement and the hydraulic medium supply arrangement result in an increase in the overall dimensions of the entire coolant pump in both the radial and axial directions.

In a first advantageous embodiment of the present invention, the actuator takes the form of a hydraulic cylinder and is disposed coaxially at the end of the drive shaft. In this context, the hydraulic cylinder is understood to be the entire assembly composed of a longitudinally movable piston and the cylinder enclosing the same. This hydraulic cylinder is preferably a single acting hydraulic cylinder, which is used to effect a pressure-induced displacement of the blocking ring to its closed position, in which the coolant outlet is closed. In this case, a compression spring, which may be disposed between the impeller and the blocking ring or inside the actuator, is used to return the blocking ring, and thus to move the single acting hydraulic cylinder in the opposite direction. Such an arrangement of a compression spring for returning the closing plate to its open position also makes it possible to create a fail-safe device which ensures that in the event of a failure of the pressure supply to the actuator, the coolant pump will always deliver sufficient coolant.

The hydraulic cylinder can be configured and arranged in different ways: One proposal is to form a running surface of the hydraulic cylinder directly in the drive shaft. In this case, the end of the drive shaft facing the impeller is configured as a hollow shaft, the inner curved surface of which forms the corresponding cylinder running surface. This makes it possible to achieve a very compact arrangement and enables the actuator to be manufactured with little difficulty. In a second, alternative option, the piston is secured on the drive shaft, and a cylinder cooperating with this piston is mounted to an overall cup-shaped guide plate forming the blocking ring, these components bounding a corresponding pressure chamber. This also provides a very compact actuator arrangement, which is suitable for mass production.

In a second embodiment of the present invention, it is proposed that the actuator take the form of a diaphragm. A suitable diaphragm would allow for a very short overall axial length. This diaphragm would be fixed to a flange part radially surrounding the drive shaft, the pressure medium flowing out of the longitudinal bore of the drive shaft pressing this diaphragm against the bottom of an also cup-shaped guide plate, so that upon deflection of the diaphragm, the guide plate is moved such that its blocking ring enters a closed position. In this case, too, a return spring is to be provided on the guide plate to return the guide plate to its open position upon removal of pressure inside of the diaphragm.

Further, for an approach whose generic features are identical to those of claim 1, it is proposed that the actuator take the form of a diaphragm and be disposed concentrically with the drive shaft in the region of the end thereof facing the impeller. Then, delivery of pressure medium to the pressure chamber provided at the diaphragm can also be via channels provided in the housing of the coolant pump. However, in addition to this option, whose implementation requires considerable technical effort, this proposal is primarily about supplying the pressurized hydraulic medium to the pressure chamber of the diaphragm via at least one longitudinal bore provided in the drive shaft. In addition to this one or more longitudinal bores, of course, transverse bores have to be provided if necessary. Such transverse bores would extend, for example, between a corresponding pressure source or a control valve and the corresponding longitudinal bore.

A refinement of this approach provides that the drive shaft receives at its end facing the impeller a substantially flange-shaped first section of the impeller, the diaphragm being fixed at its edge to the first section and supported in its central region against a cup-shaped guide plate on which is formed the blocking ring, which annularly surrounds the coolant outlet when in its blocking position. This first section of the impeller is connected to a second section axially spaced therefrom, vanes of the centrifugal pump being arranged between these two sections. The guide plate is axially movable between these two sections of the impeller and is sealed against the first section by a floating ring seal or a piston ring during its axial movement. The diaphragm is fixed in a circularly extending groove of the first section.

The aforedescribed arrangement of the guide plate within the impeller may also be provided if the actuator is embodied as a piston/cylinder unit. Moreover, the use of a diaphragm or a piston/cylinder unit as the actuator is not limited to such an arrangement of the guide plate. Instead of the guide plate, a driving element receiving the blocking ring may be spatially arranged between the pump housing and the impeller.

A refinement of this arrangement provides that a return spring is provided to counteract the movement of the guide plate in the blocking direction, which is caused by the diaphragm. Thus, the hydraulic adjusting means is a single-acting mechanism, where the diaphragm is pressurized from a pressure medium supply via a control valve, or the pressure chamber provided at the diaphragm is emptied in an unpressurized manner. Since the compression spring moves the guide plate to a position in which the coolant outlet or outlets is/are open, a fail-safe control is created in this way because in the event of a control pressure failure, it is ensured that the coolant pump will always produce a flow of coolant through the coolant circuit.

Moreover, when a diaphragm is used as the actuator, it is provided that the drive shaft receives at its end facing the impeller a substantially flange-shaped first section, and that the surface of the diaphragm facing the first section or the surface of the first section facing the diaphragm is structured. This surface structure, which is preferably in the form of grooves extending radially outwardly from the end region of the drive shaft, ensures that the pressure medium flowing in between the surfaces of the diaphragm and the section is distributed over the entire surface area. This allows the guide plate and the blocking ring formed thereon to be displaced without delay by means of the diaphragm.

Moreover, it is provided that the first section is connected by impeller vanes to a second section axially spaced therefrom, the vanes extending through openings in the guide plate. Thus, the guide plate performs a movement in an axial direction and, in its closed position, it abuts against the second section of the impeller, while in its open position, it abuts against the first section.

Finally, it is proposed that the pressure medium for the actuator in the form a diaphragm or hydraulic cylinder be delivered by a control pump disposed in the housing of the coolant pump. It is provided that this control pump is driven directly by the drive shaft. Provision is also made to provide a control valve in the coolant pump housing to connect and disconnect an operating port leading to the pressure chamber of the diaphragm or the hydraulic cylinder selectively to a pump port or a reservoir port. The pressure medium used is preferably coolant taken from the coolant circuit, so that in the potential event of leakages, it is prevented that a different pressure medium, such as lubrication oil, can mix with the coolant of the coolant circuit.

Other combinations of individual features are also possible.

BRIEF DESCRIPTION OF THE DRAWINGS

In addition, other features of the invention may be derived from the following description and from the drawings, which illustrate three exemplary embodiments of the invention in simplified form. In the drawing,

FIG. 1 is a perspective longitudinal cross-sectional view through a coolant pump according to the present invention, where an actuator is in the form of a hydraulic cylinder disposed in a drive shaft;

FIG. 2 is a perspective longitudinal cross-sectional view of a portion of a coolant pump, showing a region of its impeller with a guide plate in a closed position;

FIG. 3 shows a portion of the impeller of FIG. 2 with the guide plate in an open position;

FIG. 4 is a perspective view showing a longitudinal section through an arrangement of an impeller on a drive shaft, where the actuator takes the form of a diaphragm; and

FIG. 5 is a perspective detail view showing the region of an arrangement of an impeller on a drive shaft, where an actuator features a first impeller section having a structured surface.

DETAILED DESCRIPTION OF THE DRAWINGS

In FIG. 1, 1 designates a coolant pump including a pump housing 2 and a drive shaft 3 mounted in this pump housing 2. Preferably, drive shaft 3 is mounted in pump housing 2 by a roller bearing (not specifically shown) and receives a drive wheel 4 at one end as well as an impeller 5 at the other end. Further, the end of the drive shaft facing impeller 5 is configured as a hollow shaft 6, so that a hydraulic cylinder 7 extending coaxially with the drive shaft is formed at this end. Inside hollow shaft 6, there is formed a cylinder running surface 8, on which a hydraulic piston 9 is sealingly guided. A piston rod 10 extends from this hydraulic piston 9 and centrally through impeller 5.

Furthermore, impeller 5 is formed by a flange-shaped first section 11 and a second section 12 axially spaced therefrom, between which there extend vanes 5 a of impeller 5, the coolant drawn in centrally with respect to impeller 5 being conveyed radially outward by these vanes. Piston rod 10 extends in the direction of the longitudinal axis and has a guide plate 13 disposed thereon, which includes a disk-shaped hub 14 and an adjoining cylindrically shaped blocking ring 15. Guide plate 13 is movable by piston rod 10 in an axial direction. When guide plate 13 is in the open position, blocking ring 15 is moved into a clearance space 16 of housing 2, whereas in a blocking position shown in FIG. 1, blocking ring 15 is located in a position which covers coolant outlet 17.

The displacement of guide plate 13 is performed as a function of certain operating parameters of the internal combustion engine in which coolant pump 1 is used. This is intended to cause the coolant to heat up relatively quickly after starting the internal combustion engine, independently of the prevailing ambient temperature, in order for the internal combustion engine to reach the intended operating temperature within a short period of time.

For purposes of enabling guide plate 13 to be moved by the hydraulic cylinder 7 serving as the actuator, there is provided a control pump 18 which delivers a pressure medium from a reservoir 19 to a control valve 20. Control valve 20 is, in this case, in the form of a 3/3 way valve and is in its blocking position, in which an operating line 21 leading into the hydraulic cylinder is disconnected. Its other two positions either allow pressure medium to be delivered from control pump 18 into hydraulic cylinder 7, or to be discharged therefrom in an unpressurized manner toward reservoir 19. This makes it possible to change the respective position of guide plate 13. The guide plate is provided with openings 22, through which extend the vanes 5 a of impeller 5. Furthermore, first section 11 of impeller 5 has a seal 23 which extends around the periphery thereof and on which the blocking ring 15 formed on guide plate 13 is sealingly guided.

According to FIGS. 2 and 3, the guide plate and the actuator are of a different design than in FIG. 1, so that modified reference numerals are used for these components. Apart from that, the reference numerals substantially coincide with those in FIG. 1. In FIGS. 2 and 3, it can be seen that the impeller 5 including the two sections 11 and 12 and the vanes 5 a extending therebetween receives a guide plate 24 having a disk-shaped hub 25 and a cylindrical blocking ring 26. Moreover, guide plate 24 is formed in one piece with a cylinder 27 which, together with a hydraulic piston 28 non-rotatably mounted on drive shaft 29, forms a pressure chamber 31. Further, hydraulic piston 28 is provided with a piston ring 30, thereby sealing pressure chamber 31 within cylinder 27.

At the end face of cylinder 27, first section 11 of impeller 5 has an annular space 11 a, into which cylinder 27 is moved during displacement of guide plate 24 in an open position for coolant outlet 17 or coolant outlets 17. This position of guide plate 24 is shown in FIG. 3. A corresponding pressure build-up in the pressure chamber of cylinder 27 is effected via a longitudinal bore 32 extending through at least portions of drive shaft 29.

FIGS. 4 and 5 show a further embodiment of the present invention, where the design of the drive shaft and impeller used coincides with that in the embodiments according to FIGS. 1 through 3. In this respect, the same reference numerals are used. An important distinction over the embodiments of the invention mentioned and described above is that according to FIGS. 4 and 5, a diaphragm 33 is disposed on first section 11, an edge of this diaphragm 33 being sealingly received by an annular groove 34 of first section 11. The pressure medium delivered through longitudinal bore 32 of drive shaft 29 causes diaphragm 33 to deflect and bear against a guide plate 35, thereby moving it in an axial direction. When a blocking ring 36 is in the open position, the diaphragm 33 used assumes a position in which it rests against first section 11 over a relatively large area. In the region surrounded by diaphragm 33, first section 11 is provided with a surface structure in the form of grooves 37 leading radially outwardly from the exit region of longitudinal bore 32 in order to allow sufficient quantities of the pressure medium supplied through longitudinal bore 32 to reach the surface of diaphragm 33 that faces first section 11.

LIST OF REFERENCE NUMERALS

1 coolant pump

2 pump housing

3 drive shaft

4 drive wheel

5 impeller

5 a vanes

6 hollow shaft

7 hydraulic cylinder

8 running surface of the cylinder

9 hydraulic piston

10 piston rod

11 first section of 5

11 a annular space in 11

12 second section of 5

13 guide plate

14 disk-shaped hub of 13

15 blocking ring of 13

16 clearance space

17 coolant outlet opening

18 control pump

19 reservoir

20 control valve

21 operating line

22 openings in 13

23 seal

24 guide plate

25 disk-shaped hub of 24

26 blocking ring of 24

27 cylinder of 24

28 hydraulic piston

29 drive shaft

30 piston ring

31 pressure chamber

32 longitudinal bore

33 diaphragm

34 annular groove

35 guide plate

36 blocking ring

37 radially extending grooves

38 return spring 

1-10. (canceled)
 11. A coolant pump for a coolant circuit of an internal combustion engine, comprising: a drive wheel connected to an impeller via a drive shaft rotatably mounted in a pump housing; at least one coolant outlet being provided radially with respect to the impeller; a blocking ring movable in an axial direction and serving to change or block a cross-sectional area of the coolant outlet; and a pressure-medium-operated actuator for displacing the blocking ring, the actuator disposed concentrically with the drive shaft in a region of an end of the drive shaft facing the impeller, the actuator being secured on the end of the drive shaft, the actuator being connected to a pressure medium supply via at least one longitudinal bore provided in the drive shaft.
 12. The coolant pump as recited in claim 11 wherein the actuator takes the form of a hydraulic cylinder disposed coaxially at the end of the drive shaft.
 13. The coolant pump as recited in claim 12 wherein a cylinder running surface of the hydraulic cylinder is formed directly in the drive shaft.
 14. The coolant pump as recited in claim 11 wherein the actuator takes the form of a diaphragm.
 15. The coolant pump as recited in claim 11 wherein the drive wheel is driven by a belt drive.
 16. A coolant pump for a coolant circuit of an internal combustion engine, comprising: a drive wheel connected to an impeller via a drive shaft rotatably mounted in a pump housing; at least one coolant outlet provided radially with respect to the impeller; a blocking ring movable in an axial direction and serving to change or block a cross-sectional area of the coolant outlet; and a pressure-medium-operated actuator for displacing the blocking ring, the actuator being disposed concentrically with the drive shaft in a region of an end of the drive shaft facing the impeller, the actuator taking the form of a diaphragm.
 17. The coolant pump as recited in claim 16 wherein the drive shaft receives at the end facing the impeller a flange-shaped first section of the impeller, the diaphragm being fixed by an edge to the first section of the impeller and the diaphragm being supported in a central region against a guide plate, the blocking ring being formed on the guide plate, the blocking ring annularly surrounding the coolant outlet when in a blocking position.
 18. The coolant pump as recited in claim 17 further comprising a return spring counteracting movement of the guide plate in a blocking direction, the movement caused by the diaphragm.
 19. The coolant pump as recited in claim 16 wherein the drive shaft receives at the end facing the impeller a flange-shaped first section, and a surface of the diaphragm facing the first section or another surface of the first section facing the diaphragm is structured.
 20. The coolant pump as recited in claim 11 wherein a first section of the impeller is connected by vanes to a second section of the impeller axially spaced from the first section, the vanes extending through openings in the guide plate.
 21. The coolant pump as recited in claim 11 further comprising a control pump and a control valve disposed in the pump housing, an operating port of the control valve being connected to the longitudinal bore.
 22. The coolant pump as recited in claim 16 wherein the drive wheel is driven by a belt drive. 